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Archive for Thursday, April 5, 2007

Spring’s colorful weeds are beautiful to view but difficult to control

April 5, 2007

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Purple, pink, yellow, and white ... this is not a reference to the lilac, crabapple, forsythia or ornamental pear tree blossoms. Rather, it is a description of the color display seen right now in yards, gardens and flower beds.

The seasonal weeds dandelions, clover, henbit and chickweed are in full bloom and making quite a statement this spring. It's a show that is pretty to view but hard to control. Here is what you need to know about controlling these tenacious weeds in and around the home landscape.

Dandelion and clover are easy to identify but difficult to control. Both are perennial weeds that tend to revitalize every year during good growing conditions. Dandelions re-emerge from thick taproots and clover from underground stolons. Both can reproduce from seeds generated by the characteristic showy flowers of spring. Because of the perennial nature of these weeds, physical removal such as hand-pulling is often ineffective. Mowing can temporarily remove the blooms, but the plants will send up a new flower quickly. Once dandelions reach the white "puffball" stage, wind and mowing can scatter the seeds all over the neighborhood.

The best controls for these weeds are post-emergent broadleaf herbicides. The most effective product is Trimec, which is a common herbicide that contains a mixture of 2,4-D, MCPP and Dicamba. Together, these ingredients can knock out 90 percent of most broadleaf weeds in the home lawn. Always check the herbicide label to make sure the product you choose is safe to use where and how you wish to use it.

Do not mow the lawn for several days before and after the application. This will allow for maximum uptake and internal movement of the herbicide. Do not water for at least 24 hours after application, and do not treat if rain is expected within 24 hours.

Avoid applying broadleaf herbicides when temperatures exceed 80 degrees and/or when winds exceed 5 mph to ensure safety to both turfgrasses and nearby broadleaf shrubs and flowers.

Henbit is a rather showy spring-blooming weed. The violet flowers, born on stems 8 to 12 inches tall, are quite striking on a warm April day. They are commonly found in cultivated areas such as farmers' fields, flower beds, gardens and in the lawn. Chickweed, on the other hand, has a lower growth habit with creamy yellow blooms.

Mix the two plants together, and you can create a beautiful spring display with little effort. Keep in mind, though, as with most weeds, they can be invasive and easily take over if left unattended.

Because both weeds are self seeding, the plants that were there last year are not the same plants to reappear this year. They are, however, plants that sprouted from seeds that dropped last spring. As the days grow longer and the temperatures rise, both are in full bloom and are restarting the process.

Unfortunately, control options are limited this late in the growth cycle. Start with mechanical controls. Hoe or lightly till bare soil in the garden and around flowers, trees and shrubs. For added control, apply a fresh layer of mulch; 2 to 3 inches should be enough. For hard-to-reach or noncultivated areas, the broad-leaf weed killers Trimec and carfentrazone are the two best products to use. Spray on a sunny day when air temperatures are above 55 degrees.

Avoid spraying newly sprouted grass seed, as dieback may occur.

Likewise, avoid spraying desirable trees and shrubs. As always, read and follow all label directions. Do not expect miracle results as these plants mature and are less affected by the sprays.

- Bruce Chladny is horticulture agent at K-State Research and Extension-Douglas County. For more information, call him at 843-7058 from 8 a.m. to 5 p.m. weekdays.

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